Cooling structure for electronic boards

ABSTRACT

A cooling structure for large electronic boards with closely-spaced heterogeneous die and packages is disclosed. The assembly includes a frame having a plurality of openings. The assembly further includes a cold plate mounted to the frame. The cold plate includes at least one inlet and at least one outlet and fluid channels in communication with the at least one inlet and the at least one outlet. The assembly further includes a heat sink mounted within each of the plurality of openings which in combination with sidewalls of the openings of the frame and the cold plate form individual compartments each of which are in fluid communication with the fluid channels.

FIELD OF THE INVENTION

The invention relates to cooling structures and, more particularly, to acooling structure for large electronic boards with closely-spacedheterogeneous die and packages.

BACKGROUND

It is important in electronic circuitry and packages to adequately coollarge electronic boards that include multiple chips and packages mountedto the boards. In electronic systems, a heat sink or cold plate is apassive heat exchanger used to cool the multiple chips and packages bydissipating heat into the surrounding medium. For example, heat sinksand cold plates are used with high-power semiconductor devices such aspower transistors and optoelectronics such as lasers and light emittingdiodes (LEDs), where the heat dissipation ability of the basic device isinsufficient to moderate its temperature.

A heat sink or cold plate is designed to maximize its surface area incontact with the cooling medium surrounding it, such as the air andliquid, as well as to maximize its surface area with the chip andpackage. In conventional systems, heat sinks or cold plates withseparate air or water supplies are mounted to each chip in order toregulate heat, e.g., dissipate heat. Each heat sink or cold plate has tobe individually aligned and thereafter mounted to each chip or packageby a thermal interface material (TIM) such as thermal adhesives orthermal grease to improve performance by filling air gaps between theheat sink or cold plate and the device.

However, the use of separate cold plates or heat sinks becomes veryproblematic as chips and packages have different sizes and heights, areplaced at different distances from each other and dissipate differentlevels of power. These different sizes, heights, etc., leads to anon-optimized cooling design leading to lower supported power levels andthe need for a multitude of cooling devices. Also, each of theseseparate cold plates or heat sinks requiring their own separate coolantsupply complicates the manufacturing process and adds additional costs.

SUMMARY

In an aspect of the invention, an assembly comprises a frame having aplurality of openings. The assembly further comprises a cold platemounted to the frame. The cold plate comprises at least one inlet and atleast one outlet and fluid channels in communication with the at leastone inlet and the at least one outlet. The assembly further comprises aheat sink mounted within each of the plurality of openings which incombination with sidewalls of the openings of the frame and the coldplate form individual compartments each of which are in fluidcommunication with the fluid channels.

In an aspect of the invention an assembly comprises: a frame comprisinga plurality of openings; a heat sink mounted within each of theplurality of openings; and a cold plate that seals each of the pluralityof openings and forms a sealed compartment in combination with sidewallsof the openings and the heat sink mounted within each of the pluralityof openings, the cold plate comprising: a top plate member; a bottomplate member having a top side and a bottom side; the bottom side havinga plurality of grooves which accommodate the sidewalls of the openingsof the frame; at least one inlet port and at least one outlet port; andfluid channels in fluid communication with each of the sealedcompartments and the at least one inlet port and the at least one outletport.

In an aspect of the invention a manifold assembly comprises: a frameassembly having a plurality of sealed compartments each comprising asingle heat sink registered to an underlying chip and/or package mountedon an electronic board; a fluid channel within the frame assembly; andan inlet and an outlet associated with each of the sealed compartmentsand in fluid communication with the fluid channel, the inlet and theoutlet directing coolant over the single heat sink of each of the sealedcompartments.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIG. 1 shows a highly schematic representation of a cooling structure inaccordance with aspects of the invention.

FIG. 2 shows a cross-sectional view of the cooling structure of FIG. 1,along lines A-A.

FIG. 3 is an exploded view of the cooling structure in accordance withaspects of the invention.

FIG. 4 shows an exploded view of a cold plate assembly of the coolingstructure in accordance with aspects of the invention.

FIG. 5a shows a top view of a bottom plate member of the cold plateassembly in accordance with aspects of the invention.

FIG. 5b shows a bottom view of a bottom plate member of the cold plateassembly in accordance with aspects of the present invention.

FIG. 6 shows a cross-sectional view of the bottom plate member of FIG.5b , along line B-B.

FIG. 7 shows a partial cross sectional view of a cold plate assemblyattached to a chip/package in accordance with aspects of the invention.

DETAILED DESCRIPTION

The invention relates to cooling structures and, more particularly, to acooling structure for large electronic boards with closely-spacedheterogeneous die and packages. The cooling structure addresses theproblem of cooling large electronic boards with multiple chips andpackages mounted to the boards of various heights and mountingpositions.

More specifically, the cooling structure is designed and structured todissipate heat from chips and packages having different sizes, heights,and tilt angles, as well as placed at different distances from eachother and which dissipate different levels of power. The coolingstructure also provides a cooling solution for an electronic board withmultiple chips and packages that are spaced extremely close to eachother to enable small wire lengths and high function bandwidths.Advantageously, the cooling structure can use a single coolant supply,e.g., water or air supply, to optimize the cooling design leading tohigher supported power levels and the elimination of multiple coolingdevices. Thus, the cooling structure allows for increasing of powerlevels in the chips and the reduction in the number of individualcooling devices needed to dissipate heat from the chips and/or packageson the circuit board.

In more specific embodiments, the cooling solution comprises individualheat sinks mounted to a common frame. The individual heat sinks can bealigned over each chip or package with a TIM of minimum bondline with asingle alignment process. This is achieved by incorporating the heatsinks in the common frame. A single cold plate (e.g., manifold) ismounted to the frame and acts as a single source manifold for supplyingcoolant to the heat sinks. The heat sinks are soldered or epoxied intothe common frame over each chip or package application. The minimum TIMbondline is obtained by reflowing the solder or letting the epoxy curein place to allow the heat sink to register over each chip or package.

FIG. 1 shows a highly schematic illustration of the cooling structure inaccordance with aspects of the present invention. In embodiments, thecooling structure 10 includes a frame 15 and a cold plate 18 attached tothe frame 15. The cold plate 18 can be a hollow frame or can includecavities for directing the flow of coolant, e.g., water, to individualheat sinks 30 mounted to the frame 15. In embodiments, the frame 15 andcold plate 18 are composed of structural material such as stainlesssteel or aluminum, amongst other contemplated materials.

The cold plate 18 includes an inlet 18′ and an outlet 18″ for the flowof coolant through the cold plate 18 (e.g., manifold) and over the heatsinks 30 mounted to the frame 15. The inlet 18′ and the outlet 18″ canbe placed at various locations around the cold plate 18 as describedfurther herein. The coolant can be water or air supply or other knowncoolant, which will flow over the heat sinks 30 as further describedbelow.

In embodiments, the frame 15 is mounted to a circuit board 20 having avariety of chips and or packages of different sizes, shapes, heights,etc., as represented by reference numeral 25. The circuit board 20 canbe any conventional circuit board such as, e.g., a glass board with anarray of chips and packages 25 closely spaced apart. A plurality of heatsinks 30 are soldered or epoxied within openings provided within theframe 15, which also serves to allow coolant to be supplied to each ofthe heat sinks 30 in separate compartments as provided from the coldplate 18. The heat sinks 30 can be any heatsink material such as copperor aluminum; although other materials are also contemplated by thepresent invention. The heat sinks 30 can include fins 30a of variousdimensions. In embodiments, the heat sinks 30 are soldered or epoxied tothe frame 15, directly aligned with each of the electronic chips orpackage 25 as shown representatively within the dashed circle atreference numeral 35.

As should be understood by those of skill in the art, a single heat sink30 can be mounted to multiple chips and/or packages which are placedvery closely together. It should be further understood that each of theheat sinks 30, as described herein, can be adjusted to a specific heightand tilt angle of each of the multiple chips and/or packages 25 mountedon the circuit board 20, within the frame 15. Also, each of the heatsinks 30 can be aligned to each of the chips and/or packages in a singlealignment process using the frame 15. The heat sinks 30 are alsodesigned to have a same dimension, e.g., width and length, of each ofthe multiple chips and/or packages 25 mounted on the circuit board 20 toensure optimized contact and hence optimized heat dissipation.

FIG. 2 shows a highly schematic cross-sectional view of the coolingstructure 10 of FIG. 1, along lines A-A. As shown in this crosssectional view, the frame 15 includes a plurality of openings 15 a. Asdescribed further herein, each of the heat sinks 30 is mounted into theindividual openings 15 a by solder or epoxy 40. The cold plate 18 ismounted to the frame 15 and supplies coolant to each heat sink 30 withineach individual opening 15 a. In this way, a single frame assembly canbe used as a manifold to supply coolant to a multitude of different heatsinks 30.

The cold plate 18 will be sealed to the frame 15 by epoxy or solder,such that each heat sink 30 will be provided in a separate, sealedcompartment which can accommodate the flow of coolant over each of theheat sinks 30. The coolant can flow through the cold plate 18 throughthe inlets 18′ and outlets 18″, and directed into each of the sealedcompartments through a network of channels and openings, as furtherdescribed herein. In this way, a single coolant supply can be used toefficiently dissipate heat from a plurality of chips and packages 25.

As further shown in FIG. 2, the heat sink 30 includes a plurality offins 30 a. The fins 30 a can be of a variety of different shapes suchas, e.g., cuboidal or cylindrical pin fins or channels that may beparallel or trapezoidal, etc. The heat sink 30 is bonded to the chipand/or package 25 by a thermal interface material (TIM) 45. The TIM 45has a minimum TIM bondline obtained by loading the heat sinks 30 againstthe chips or packages 25. By way of example, the minimum TIM bondline isobtained by reflowing the solder or letting the epoxy cure in place toallow the heat sink 30 to register over each chip or package 25. Inembodiments, the TIM 45 can be thermal greases, gels, compounds,adhesives, pastes or metal interfaces, for example.

FIG. 3 is an exploded view of a portion of the cooling structure inaccordance with aspects of the present invention. As shown in thisrepresentation, the frame 15 includes a plurality of openings 15 a,which are sized to accommodate separate heat sinks 30. The openings 15 acan include a stepped portion (ledge) for mounting of the heat sinks 30,as described further herein. The openings 15 a and hence the heat sinks30 are sized to each of the different chips and/or packages 25 mountedon the board 20. In this way, a single frame 15 can be used to (i) alignand mount plural heat sinks 30 to plural chips and packages and (ii)provide a single coolant assembly for plural heat sinks 30.

FIG. 4 shows an exploded view of the cold plate 18 in accordance withaspects of the invention. The cold plate 18 includes a top plate member18 a and bottom plate member 18 b which are sealed together to form thecold plate 18. The bottom plate member 18 b includes a plurality ofinlet and outlet fluid channels or cavities 50 a, 50 b connectedrespectively to the inlets 18′ and outlets 18″ for the flow of coolant.The top plate member 18 a is sealed to the bottom plate member 18 b toensure that the coolant remains within the fluid channels 50 a, 50 b,which is directed to each of the individual openings (e.g., heat sinks30) by way of slots or openings as described herein.

FIG. 5a shows a top view of the bottom plate member 18 a of the coldplate 18; whereas, FIG. 5b shows a bottom view of the bottom platemember 18 a of the cold plate 18. As shown in these views, the top ofthe bottom plate member 18 a includes a plurality of inlet channels 50 aand a plurality of outlet channels 50 b, connected to the inlet 18′ andoutlet 18″, respectively. Each of these channels 50 a, 50 b includeinlet openings (ports) 60 a and outlet openings (ports) 60 b, associatedwith a separate compartment 70.

As should be understood, the separate compartments 70 will be formed bythe sidewalls of the openings 15 a, the underside surface of the bottomplate member 18 b and the heat sink 30, itself. The compartment 70 willbe watertight due to the combination of the solder or epoxy connectionof the heat sink 30 to the sidewalls of the opening 15 a, as well as theconnection of the bottom plate member 18 b to the cold plate 18. Coolantwill be directed through each of these compartments 70 (and hence incontact with the heat sinks) as shown representatively by the arrowspassing from the (i) inlet 18′, (ii) inlet channels 50 a, (iii) inletopenings (ports) 60 a to the compartment 70, (iii) outlet openings(ports) 60 b from the compartment 70 and (iv) outlet channels 50 b.

FIG. 5b shows the underside surface of the bottom plate member 18 b. Theunderside surface includes a plurality of recesses or grooves 55. Thesegrooves 55 correspond to the sidewalls of the openings of the frame 15,e.g., openings 15 a of the frame 15. In embodiments, the sidewalls ofthe openings 15 a will be soldered or epoxied within the grooves 55 toensure that each of the heat sinks 30 will be provided in a separate,sealed compartment 70. In embodiments, the grooves 55 can accommodate aseal ring, e.g., O-ring seal, epoxy or solder, as shown representativelyat reference numeral 65.

FIG. 6 shows a cross-sectional view of the bottom plate member 18 balong line B-B of FIG. 5b . As shown in this view, each of the fluidchannels 50 a, 50 b will include inlet openings 60 a and outlet openings60 b so that coolant can flow through each separate compartment, e.g.,holding separate heat sinks. That is, the fluid channels 50 a, 50 b willbe in fluid communication with the respective inlet openings 60 a andoutlet openings 60 b for each compartment 70 (as shown in FIG. 5a ),which allows the coolant, e.g., water or air supply, to flow into theindividual compartments, e.g., over the heat sinks 30 within thecompartments. The inlet openings 60 a and outlet openings 60 b will beprovided within the confines of the grooves 55. In this way, a singleframe assembly, e.g., frame 15 for holding the heat sinks and cold plate18 for supply coolant to the individual heat sinks, can be used as amanifold to provide a single coolant supply to a multitude of heat sinksto dissipate heat from multiple chips and packages having differentsizes and heights, placed at different distances from each other.Accordingly, the frame assembly described herein optimizes the coolingdesign leading to higher supported power levels and the elimination ofmultitude of cooling devices.

FIG. 7 shows a partial cross-sectional view of frame assembly andrelated components, attached to a chip/package in accordance withaspects of the invention. More specifically, as shown in FIG. 7, theheat sink 30 (with fins 30 a) is provided within an opening 15 a of theframe 15. In embodiments, the heat sink 30 can be mounted to a ledge 15a′ of the opening 15 a by an epoxy or solder, as represented byreference numeral 40. As noted already herein, the minimum TIM bondline45 can be obtained by reflowing the solder or letting the epoxy cure inplace to allow the heat sink 30 to register over each chip or package25. The chip or package 25 is shown to be mounted to the circuit board20 by solder connections 25 a.

As further shown in FIG. 7, the heat sink 30 is provided within a sealedcompartment 70 formed partly by the cold plate 18. The sealedcompartment 70 can be watertight, as defined by the sidewalls of theopening 15 a of the frame 15 and the underside surface of the cold plate18, e.g., bottom plate member 18 b of the cold plate 18, and the heatsink 30 sealed to the sidewalls. The bottom plate member 18 b is mountedto the sidewalls of the opening 15 a by mounting of the sidewalls 15 a″within the grooves 55. In embodiments, the sidewalls of the openings 15a will be soldered or epoxied to the grooves 55 as shown at referencenumeral 65. An O-ring can also be placed within the groove 55. In eitherof these different embodiments, the compartment will be watertight.

The bottom plate member 18 b is sealed to the top plate member 18 athereby forming fluid channels 50 a, 50 b, which are in fluid connectionwith the inlets 60 a and outlets 60 b to each separate compartment 70.The combination of the fluid channels 50 a, 50 b with the inlets 60 aand outlets 60 b will direct coolant through each of the individualsealed compartments 70. In this way, the frame assembly described hereinacts as a manifold for directing fluid to each individual compartmentand over each of the individual heat sinks 30.

The method(s) as described above is used in the fabrication ofintegrated circuit chips. The resulting integrated circuit chips can bedistributed by the fabricator in raw wafer form (that is, as a singlewafer that has multiple unpackaged chips), as a bare die, or in apackaged form. In the latter case the chip is mounted in a single chippackage (such as a plastic carrier, with leads that are affixed to amotherboard or other higher level carrier) or in a multichip package(such as a ceramic carrier that has either or both surfaceinterconnections or buried interconnections). In any case the chip isthen integrated with other chips, discrete circuit elements, and/orother signal processing devices as part of either (a) an intermediateproduct, such as a motherboard, or (b) an end product. The end productcan be any product that includes integrated circuit chips, ranging fromtoys and other low-end applications to advanced computer products havinga display, a keyboard or other input device, and a central processor.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed:
 1. A manifold assembly, comprising: a frame assemblyhaving a plurality of sealed compartments each comprising a single heatsink registered to an underlying chip and/or package mounted on anelectronic board; a fluid channel within the frame assembly; and aninlet and an outlet associated with each of the sealed compartments andin fluid communication with the fluid channel, the inlet and the outletdirecting coolant over the single heat sink of each of the sealedcompartments.
 2. The manifold assembly of claim 1, wherein the frameassembly includes: a plurality of openings in a frame; and a cold plateassembly sealed to sidewalls of the openings of the bottom plate, fluidchannels in the cold plate which includes the inlet and outlet for eachof the sealed compartments.
 3. The manifold assembly of claim 2, whereinthe heat sink is mounted within each of the plurality of openings of theframe and in combination with sidewalls of the openings of the frame andthe cold plate assembly form individual compartments each of which is influid communication with the fluid channels.
 4. The manifold assembly ofclaim 2, wherein the cold plate assembly includes grooves structured toaccommodate the sidewalls of the plurality of openings of the frame formounting of the frame to the cold plate.
 5. The manifold assembly ofclaim 4, wherein each individual compartment is a sealed compartment. 6.The manifold assembly of claim 4, further comprising an o-ring withinthe grooves.
 7. The manifold assembly of claim 4, further comprisingepoxy or solder within the grooves to mount the cold plate assembly tothe frame.
 8. The manifold assembly of claim 2, wherein the cold plateassembly comprises a top plate member and a bottom plate member, thebottom plate member comprises grooves and the top plate member forms asurface of the fluid channels.
 9. The manifold assembly of claim 2,wherein the heat sink includes fins which are one of cuboidal,cylindrical pin fins, channels that are parallel and trapezoidal. 10.The manifold assembly of claim 9, wherein the heat sink is provided ineach of the plurality of openings attached to the sidewalls of theopenings.
 11. The manifold assembly of claim 10, wherein the heat sinkin each of the plurality of openings is registered and spans over atleast one underlying chip or package mounted on an electronic board andmounted thereon by a thermal interface material (TIM).
 12. The manifoldassembly of claim 2, wherein the cold plate assembly seals each of theplurality of openings and forms a sealed compartment in combination withthe sidewalls of the openings and the heat sink mounted within each ofthe plurality of openings, the cold plate assembly comprising: a topplate member; a bottom plate member having a top side and a bottom side;the bottom side having a plurality of grooves which accommodate thesidewalls of the openings of the frame; at least one inlet port and atleast one outlet port; and fluid channels in fluid communication witheach of the sealed compartments and the at least one inlet port and theat least one outlet port.